Memory cells may include, for example, phase-change random-access memory (PCRAM), resistive random-access memory (RRAM or ReRAM), magnetic random-access memory (MRAM), and/or fuse/anti-fuse devices. Selector devices may include, for example, diodes (e.g., unipolar or bipolar), and other 2-terminal (e.g., ovonic threshold switch (OTS)) or 3-terminal devices (e.g. field-effect transistors (FETs) and bipolar junction transistors (BJTs)).
RRAM devices have a three-layer structure of a top electrode, switching medium and bottom electrode. A resistance switching mechanism utilizes a filament formed in the switching material upon application of a voltage to the two electrodes. With RRAM technology, a silicon-based switching material can be used for metallic filament formation. For example, filamental resistive memory has been demonstrated with amorphous silicon/crystalline silicon (a-Si/c-Si) heterojunctions.
RRAM devices can be stacked in a three-dimensional (3D) configuration. Commercially available 3D RRAM devices include Crossbar™ ReRAM, from Crossbar, Inc. of Santa Clara, Calif., and 3D XPoint™, from Intel Corporation of Santa Clara, Calif. Storage in the 3D RRAM devices is based on resistance changes in a stackable cross-gridded data access array.
Back-end-of-line (BEOL) requirements for selector devices to enable 3D stacking can include, for example, selector device fabrication temperatures below ˜400° C. to prevent damage to BEOL metal lines, and after fabrication, selector devices being able to withstand temperatures of ˜400° C., which may be the metallization temperature of upper layers.
There is a need for resistive memory devices, such as RRAM and 3D RRAM, and methods of fabricating same, which are compatible with BEOL structures and techniques.